Round 1: 64.
and
. The 64 characters have some
really obscene hitstun, the ability to just massacre shields and have silly confirms like
jab grabs (which even 64 CPUs use). Oh and both have some absurd hitboxes like both their up tilts:
Sure, the saving grace is that they won't have as many moves, dodges etc. as their later counterparts, but one hit and you'll likely to take like 80 %.
Round 2: Brawl part 1.
and
. Ah yes, the time when Olimar had 6 Pikmin and Diddy had 2 peels (incl. an infinite off of the peels). Not only are those two hard to hit generally, but momentum cancelling allows them to survive a lot longer than expected and Diddy has the best shield in Brawl. Diddy can also glide toss the peels while Olimar's Pikmin Order has some very generous super armor in Brawl. There's some solace with them tripping, but they're going to be a hassle.
Round 3: Smash 4... but with Custom Moves.
and
. Why these two? Well, Villager
with custom moves has access to Timber Counter, a long lasting sapling that trips constantly, plus bigger Lloid Rockets and exploding balloons. He's a major hassle to even deal with. DK with custom moves turns into Aang, with Airbender versions of Giant Punch and Up B + Firebender version of Down B. All three of those can kill earlier than normal - oh and did I mention that Smash 4's Rage mechanic straight up is overpowered?
Round 4: Maylay.
and
. No real need for introductions to either of them, TerminalMontage solidified the memetic image of them dashdancing all over the ****ing place and Marth's infamous grab range. Also, they have access to shield dropping through platforms and edgecancelling off of them, making them difficult to challenge on platforms.
Round 5: Smash 4 part 2.
and
. No real need to introduce 4's Bayonetta, but a less talked about aspect of hers is that most of her aerials could kill much sooner than her Ultimate counterparts. Cloud's 4 counterpart not only had a huge N-Air, but oprresive U-Air / D-Air and permanent Limit Break (until he uses it or dies). They're going to be extremely difficult to challenge.
Round 6 (Final Bosses): Brawl part 2. Oh ****.
and
. Brawl Meta Knight is legendary and with good reason. The
TV tropes page for game breaker lists no less than 8 absurdly strong and spammable attacks (he's listed as a Game Breaker in Subspace, Multi Man and Boss Fights too!). Not to mention the ability to stall if needed with how safe his attacks generally are. Brawl ICies is the definition of chainthrowing - with their version being infinite - and they're able to wall people out consistently with a powerful Blizzard / Ice Shot.
Have fun.